The present invention relates to thermal insulation systems for buildings and, more particularly, to insulation systems for electrical outlet assemblies in exterior walls.
An important source of heat loss in conventional building structures is air infiltration through gaps and cracks in the walls and in the framing around windows and doors. It has been empirically established that approximately 20% of all air infiltration in residential buildings is attributable to losses through electrical outlets on the inside of exterior walls. Electrical outlet assemblies, including the electrical boxes in which they are disposed, comprise a gap in the insulation system of conventional buildings through which heated air is readily lost from the building at the same time that cold air is admitted into the structure. Furthermore, these assemblies form a path for large heat conduction losses through the wall and a means through which moisture may permeate into wall insulation materials. In order to improve the thermal efficiency of residential buildings and save energy, the provision of an insulation system for electrical outlets is a logical expedient.
Prior patents, i.e., U.S. Pat. No. 1,713,101, have disclosed the use of plates of electrical insulation disposed behind the faceplate of an electrical switch. However, these insulation plates have been formed of hard rubber or bakelite materials, which materials, although they possess good electrical insulation properties, are poor thermal insulators. Furthermore, these materials do not have the properties of compressibility and resilience necessary to properly seal the electrical switch box against air infiltration. Other patents, i.e., U.S. Pat. No. 3,028,467, have disclosed the use of sealing cover plates in conjunction with switch boxes. However, these plates have not been disposed in front of the switch faceplate, they have not been designed to provide a barrier to thermal conduction, and their application has necessarily been limited to electrical switches which do not have electrical plug slots. Another series of patents, i.e., U.S. Pat. Nos. 2,641,627; 2,710,382; 3,201,740; and 3,845,234, have disclosed cover plates for the electrical plug slots of electrical receptacles to protect against electrical shock. However, these plates have generally been of limited size sufficient only to cover the slots and the electrical socket elements themselves; and, consequently, they have been inadequate to provide an effective barrier against thermal conduction or seal the outlet assembly against air infiltration.